CHAPTER XII 
COCCIDIOSIS 
Characterization. Coccidiosis is primarily a disease of the in- 
testinal tract. In young chicks it may also affect the liver and 
in geese, the causative organism may be localized in the kidneys. 
It is one of the greatest scourges of fowls, pigeons and turkeys. 
Etiology. The organism causing coccidiosis is designated Hi- 
meria (Cocciditum) avium and belongs to a class of protozoan para- 
sites known as sporozoa. The organism is included in the animal 
kingdom and reproduces by both sexual and asexual processes. The 
parasite was long known as Coccidiwm avium but owing to the rules 
of priority in zoological nomenclature, the familiar name of the 
genus Coccidiwm has been replaced by Himeria. 
In the odcyst or resistant stage, the one most easily recognized on 
microscopic examination of the intestinal contents, the protozoan 
generally appears as an oval body containing a central granular 
mass surrounded by a highly refractile zone with a double con- 
toured border. The size varies from 25 microns to 35 microns in 
length and from 15 microns to 20 microns in breadth. 
Life history of Eimeria avium. The life history has been ad- 
mirably worked out by Fantham. There are two principal stages in 
the life cycle, a stage of asexual multiplication, termed schizogony, 
and a stage of sexual reproduction in which male and female elements 
unite to form resistant bodies for life outside the animal cells. In 
the asexual stage the newly formed parasites pass from one cell to 
another, and it is during this cycle that the great destruction of in- 
testinal mucosa occurs. 
-(a) The young, growing parasite. The odcyst reaches the duo- 
denum cf the bird through the medium of the food or water. Here 
the tough cyst wall is softened and four small oval bodies or spores 
are released. From each of these are given off two actively motile 
vermiform bodies with one end more pointed than the other, which 
vary from 7 to 10 microns in length. These are the primary infect- 
ing germs or sporozoites (fig. 13 A). The sporozoite passes into an 
epithelial cell lining the first portion of the intestine where it curls 
on itself (fig. 13 B), takes on a spherical outline (fig. 13 C) and be 
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